The present invention is related to prosthetic heart valve replacement, and more particularly to devices, systems, and methods for transcatheter delivery of collapsible prosthetic heart valves.
Prosthetic heart valves that are collapsible to a relatively small circumferential size can be delivered into a patient less invasively than valves that are not collapsible. For example, a collapsible valve may be delivered into a patient via a tube-like delivery apparatus such as a catheter, a trocar, a laparascopic instrument, or the like. This collapsibility can avoid the need for a more invasive procedure such as full open-chest, open-heart surgery.
Collapsible prosthetic heart valves typically take the form of a valve structure mounted on a stent. There are two types of stents on which the valves structures are ordinarily mounted: a self-expanding stent and a balloon-expandable stent. To place such valves into a delivery apparatus and ultimately into a patient, the valve must first be collapsed or crimped to reduce its circumferential size. These collapsible and re-expandable prosthetic heart valves can then be implanted transapically or percutaneously through the arterial system, such as through the femoral artery.
When a collapsed prosthetic valve has reached the desired implant site in the patient (e.g., at or near the annulus of the patient's heart valve that is to be replaced by the prosthetic valve), the prosthetic valve can be deployed or released from the delivery apparatus and re-expanded to full operating size. For balloon-expandable valves, this generally involves releasing the entire valve, assuring its proper location, and then expanding a balloon positioned within the valve stent. For self-expanding valves, on the other hand, the stent automatically begins to expand as the sheath covering the valve is withdrawn.
In conventional delivery systems for self-expanding aortic valves, for example, after the delivery system has been positioned for deployment, the annulus end of the valve is typically unsheathed and expanded first, while the aortic end of the valve remains sheathed. Once the annulus end of the valve has expanded, it may be determined that the valve needs to be repositioned in the patient's aortic annulus. To accomplish this, a user (such as a surgeon or an interventional cardiologist) typically resheathes the annulus end of the valve, so that the valve can be repositioned while in a collapsed state. After the valve has been repositioned, the user can again release the valve.
As stated above, collapsible prosthetic heart valves may be delivered to the valve annulus, and particularly the aortic valve annulus, either transfemorally or transapically, as well as by other percutaneous procedures. In transfemoral valve implantation, the collapsible prosthetic heart valve is introduced through the femoral artery and is ultimately delivered in a retrograde manner through the aortic arch to the native aortic valve annulus. In transapical valve implantation, the collapsible prosthetic heart valve is delivered in an antegrade fashion through the apex of the heart to the native aortic valve annulus.
In transapical valve implantation, it would be preferable if the axis of the entry point at the apex of the heart was coaxial with the axis of the annulus of the aortic heart valve. This would allow a straight transapical valve delivery device to enter the left ventricle through the apex of the heart and move in a straight line directly through the center of the annulus area of the aortic heart valve. However, in patients with diseased hearts and heart valves, there can be a mismatch of up to 30 or 40 degrees between the apical and annular axes. Moreover, tissue structures within the heart may interfere with a straight path from the apex of the heart to the center of the aortic valve annulus. These structural issues can add additional difficulty to the process of correctly aligning a prosthetic heart valve at the site of implantation.
Despite the various improvements that have been made to the collapsible prosthetic heart valve delivery process, conventional delivery devices, systems, and methods suffer from some shortcomings. For example, prosthetic valve delivery devices have not yet fully addressed patient specific mismatches between the apical and annular axes or the heart or the presence of interfering tissue structures.
There therefore is a need for further improvements to the devices, systems, and methods for transcatheter delivery of collapsible prosthetic heart valves, and in particular, self-expanding prosthetic heart valves. Among other advantages, the present invention may address one or more of these needs.